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兰州盆地位于青藏高原与黄土高原过渡地带,晚新生代全球降温和青藏高原的构造隆升对这一地区的温度、降水和高程产生了显著的影响。利用红度-温度和磁化率-降水转换函数并结合古生物、地层地貌资料对兰州盆地过去8Ma的温度、降水和高度的半定量重建,结果表明:8.3～3.5Ma兰州盆地气候较为暖湿,期间经历了3个阶段两次显著的降温和变干过程,年均温度从16.7±2.9℃降低到11.9±3.2℃,年均降水从1150±350mm减小至500±100mm,这一时期盆地的冷干化可能受到全球降温和高原隆升的双重影响,但盆地海拔可能一直维持在1000m以下;3.5～1.7Ma盆地经历了青藏运动的A,B和C三幕,形成了一级山麓剥蚀面,代表了兰州盆地演化的新高度,海拔可能达到了1400～1600m,年均温度变为6.0±2.5℃,年均降水为240±40mm;1.70～0.45Ma山麓剥蚀面海拔达到1791～1991m,年均温度和年均降水分别为4.7±3.8℃和145±135mm;0.45～0Ma期间青藏高原再次隆起使兰州盆地继续抬升,达到现今的高度,并最终形成了目前的地貌格局,年均温度为5.2±4.8℃,年均降水为363±237mm,现今的气候特征也由此形成。
The Lanzhou Basin is located in the transitional zone of the Qinghai-Tibet Plateau and the Loess Plateau. The late Cenozoic global cooling and the tectonic uplift of the Qinghai-Tibet Plateau have a significant impact on the temperature, precipitation and elevation in this area. Semi-quantitative reconstruction of temperature, precipitation and altitude over the past 8 Ma in the Lanzhou basin was carried out using the redness-temperature and magnetic susceptibility-precipitation transfer function combined with palaeontology and stratigraphic data. The results show that the climate in Lanzhou basin from 8.3 to 3.5 Ma is warmer and wetter, After three significant cooling and drying processes, the average annual temperature dropped from 16.7 ± 2.9 ℃ to 11.9 ± 3.2 ℃, and the average annual precipitation decreased from 1150 ± 350mm to 500 ± 100mm. During this period, the cold Drying may be doubled by the global cooling and uplift of the plateau, but the basin elevation may have been maintained below 1000m. The 3.5-1.7Ma basin experienced three episodes A, B and C of the Qinghai-Tibet movement, forming a first- Representing the new height of Lanzhou basin evolution, the elevation may reach 1400 ~ 1600m, the average annual temperature becomes 6.0 ± 2.5 ℃, the average annual rainfall of 240 ± 40mm; 1.70 ~ 0.45Ma foothills eroded surface elevation of 1791 ~ 1991m, annual average During the period from 0.45 to 0 Ma, the re-uplift of the Qinghai-Xizang Plateau continued to uplift the Lanzhou basin to reach the present level and finally formed the present geomorphological pattern with an annual average temperature of 5.2 ± 4.8 ℃, average annual decline Was 363 ± 237mm, today’s climate characteristics are thus formed.